Magnetoelectronic devices, spin electronic devices, and spintronic devices are synonymous terms for devices that make use of effects predominantly caused by electron spin. Magnetoelectronics are used in numerous information devices to provide non-volatile, reliable, radiation resistant, and high-density data storage and retrieval. The numerous magnetoelectronic information devices include, but are not limited to, Magnetoresistive Random Access Memory (MRAM), magnetic sensors, and read/write heads for disk drives.
Typically an MRAM includes an array of magnetoresistive memory elements (bits). Each magnetoresistive memory element typically has a structure that includes multiple magnetic layers separated by various non-magnetic layers, such as a magnetic tunnel junction (MTJ), and exhibits an electrical resistance that depends on the magnetic state of the device. Information is stored as directions of magnetization vectors in the magnetic layers. Magnetization vectors in one magnetic layer are magnetically fixed or pinned, while the magnetization direction of another magnetic layer may be free to switch between the same and opposite directions that are called “parallel” and “antiparallel” states, respectively. Corresponding to the parallel and antiparallel magnetic states, the magnetic memory element has low and high electrical resistance states, respectively. Accordingly, a detection of the resistance allows a magnetoresistive memory element, such as an MTJ device, to provide information stored in the magnetic memory element. There are two completely different methods used to program the free layer: field switching and spin-torque switching. In field-switched MRAM, current carrying lines adjacent to the MTJ bit are used to generate magnetic fields that act on the free layer. In spin-torque MRAM, switching is accomplished with a current pulse through the MTJ itself. The angular momentum carried by the spin-polarized tunneling current causes reversal of the free layer, with the final state (parallel or antiparallel) determined by the polarity of the current pulse. Spin-torque transfer is known to occur in MTJ devices and giant magnetoresistance devices that are patterned or otherwise arranged so that the current flows substantially perpendicular to the interfaces, and in simple wire-like structures when the current flows substantially perpendicular to a domain wall. Any such structure that exhibits magnetoresistance has the potential to be a spin-torque magnetoresistive memory element. In some device designs the free magnetic layer of the MTJ may have stable magnetic states with magnetization in the film plane, and in other cases the stable states have magnetization perpendicular to the plane. In-plane devices typically have their magnetic easy axis defined by the in-plane shape of the free layer and perpendicular devices typically employ materials with a perpendicular magnetic anisotropy (PMA) that create a perpendicular easy axis.
Bit pattern fidelity is extremely important for MRAM performance. An MTJ bit etch comprises a top electrode etch (primarily chemical) and a magnetic stack etch (primarily physical). A hard mask of photoresist and tetra-ethyl-ortho-silane (TEOS) does not perform well under these two etches. The bit shape is changed during the top electrode etch and loses its pattern fidelity. This change in bit shape may be reduced by the use of a thick photoresist for high aspect ratio bits, but the thick photoresist has a tendency to collapse causing irregular bit shape.
Accordingly, there is a need for a hard mask and a method of manufacturing a magnetoresistive-based device providing high bit pattern fidelity. Furthermore, other desirable features and characteristics of the exemplary embodiments will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.